We define a new measurement of entanglement, the entanglement of projection, and find that it is natural to write the entanglements of formation and assistance in terms of it. Our measure allows us to describe a new class of quantum erasers which restore entanglement rather than just interference. Such erasers can be implemented with simple quantum computer components. We propose realistic optical versions of these erasers.
Wave-particle duality is a bizarre feature at the heart of quantum mechanics which refers to the mutually exclusive dual attributes of quantum objects as the wave and the particle. Quantum eraser presents a counterintuitive aspect of the wave-particle duality. In this work, we show that quantum eraser can be quantitatively understood in terms of the recently developed duality--entanglement relation. In other words, we show that wave-particle-entanglement triality captures all the physics of the quantum erasure. We find that a controllable partial erasure of the which-path information is attain…
We utilize IBM's quantum computers to perform a full quantum simulation of the optical quantum eraser (QE) utilizing a Mach-Zehnder interferometer with a variable partially-polarizing beam splitter (VPPBS) at the input. The use of the VPPBS motivates us to introduce the entangled quantum eraser, for which the path information is erased using a Bell-basis measurement. We also investigate the behavior of the wave aspect, i.e., the quantum coherence, as well as the particle character, represented by the predictability and entanglement, as delineated in complete complementarity relations (CCRs). A…
Quantum entanglement is known as a unique feature of quantum mechanics, which cannot be obtained from classical physics. Recently, a coherence interpretation has been conducted for the delayed-choice quantum eraser using coherent photon pairs, where phase-locked symmetric frequency detuning between paired photons plays an essential role for selective measurement-caused nonlocal correlation. Here, a macroscopic version of the nonlocal correlation is presented using orthogonally polarized optical fields in a continuous wave quantum eraser scheme in a Mach-Zehnder interferometer (MZI). The result…
Entanglement and photoelectron holography in dissociative photoionization: molecular quantum eraser
Friedrich Schiller University（弗里德里希·席勒大学）；Institute for Optics and Quantum Electronics, Friedrich Schiller University（弗里德里希·席勒大学光学与量子电子学研究所）；Leibniz University Hannover（汉诺威莱布尼茨大学）；Institute of Theoretical Physics, Leibniz University Hannover（汉诺威莱布尼茨大学理论物理研究所）；Institute of Condensed Matter Theory and Optics, Friedrich Schiller University（弗里德里希·席勒大学凝聚态理论与光学研究所）；University of Sarajevo, Faculty of Science（萨拉热窝大学理学院）；Academy of Sciences and Arts of Bosnia and Herzegovina（波斯尼亚和黑塞哥维那科学与艺术学院）；Helmholtz Institute Jena（耶拿赫尔姆霍兹研究所）
Multi-dimensional entanglement transport through single-mode fibre
全球量子网络需要在长距离上分布纠缠态，使用纠缠偏振态已经证明了重大进展，在自由空间中达到约1200公里，在光纤中达到100公里。将更多的信息打包到每个光子中需要具有更高维度的希尔伯特空间，例如，光的空间模式。然而，空间模式纠缠传输需要定制的多模光纤，并受到退相干引起的模式耦合的限制。在这里，我们传输多维纠缠态下传统的单模光纤（SMF）。我们通过纠缠双光子对的自旋-轨道自由度来实现这一点，将偏振（自旋）光子向下传递到SMF，同时与另一个光子访问多维轨道角动量（轨道）子空间。我们展示了在多个2x2维度上250 m SMF下的高保真混合纠缠保持，演示了量子密钥分发协议、量子态层析成像和量子擦除器。这项工作提供了一种替代的方法，空间模式纠缠传输，促进部署在传统的光纤网络。
Detecting high-dimensional entanglement by randomized product projections
School of Mathematics and Statistics, Beijing Technology and Business University（北京工商大学数学与统计学院）；School of Mathematical Sciences, Capital Normal University（首都师范大学数学科学学院）；Collaborative Innovation Center of Extreme Optics, Shanxi University（山西大学极端光学协同创新中心）；Hefei National Laboratory（合肥国家实验室）
Quantum entanglement generation is generally known to be impossible by any classical means. According to Poisson statistics, coherent photons are not considered quantum particles due to the bunching phenomenon. Recently, a coherence approach has been applied to interpret quantum features such as the Hong-Ou-Mandel (HOM) effect, Franson-type nonlocal correlation, and delayed-choice quantum eraser, where the quantum feature is due to basis-product superposition at the cost of 50 % photon loss. For this, it has been understood that a fixed sum-phase relation between paired photons is the bedrock …
We develop a measurement operator formalism to handle quantum nondemolition (QND) measurement induced entanglement generation between two atomic gases. We first derive how the QND entangling scheme reduces to a positive operator-valued measure, and consider its limiting case when it can be used to construct a projection operator that collapses the state to a total spin projection state. We then analyze how a stroboscopic sequence of such projections made in the x and z basis evolves the initial wave function. Such a sequence of QND projections can enhance the entanglement between the atomic en…
The basic \emph{entanglement swapping protocol} allows to project two qubits, which have never interacted, onto a maximally entangled state. For deterministic swapping, the key ingredient is the maximal entanglement that was initially contained in two pairs of qubits and the capacity of projecting onto a Bell basis. Thus the basic and deterministic entanglement swapping scheme involves three maximal level of entanglement. In this work we propose probabilistic entanglement swapping processes performed with different amounts of initial entanglement. Besides that we suggest a non Bell measuring-b…
Compressibility of genuine multipartite entanglement under the Hadamard map
Faculty of Mathematics and Physics, Charles University（查理大学数学与物理学院）；Technische Universität Wien（维也纳工业大学）；Naturwissenschaftlich-Technische Fakultät, Universität Siegen（锡根大学自然科学技术学院）
We study the level-spacing statistics in the entanglement spectrum of output states of random universal quantum circuits where qubits are subject to a finite probability of projection to the computational basis at each time step. We encounter two phase transitions with increasing projection rate: The first is the volume-to-area law transition observed in quantum circuits with projective measurements; The second separates the pure Poisson level statistics phase at large projective measurement rates from a regime of residual level repulsion in the entanglement spectrum within the area-law phase,…
Recently, it was shown that quantum entanglement is an indispensable part of the duality behavior of light. Here, we report a surprisingly intimate connection between the stereographic projection and the duality--entanglement nature of a single photon. We show that, the duality--entanglement relation [Optica \textbf{5}, 942 (2018)], naturally emerges from the stereographic projection geometry. We demonstrate that this geometry is complementarity sensitive; in the sense that, it is sensitive to the particle nature, wave nature, and entanglement nature of a single photon.
